I use Mobil 1 75W-90 currently and I've run Amsoil Series 2000 75W-90 in the rear-end of my 95 E320. You'll be fine with either of those or any other GL-4 or -5 for that matter if you don't like synthetics. And no they're not limited slip, I wish they were though!!!
It will take just a little over 1 quart to fill it so make sure to buy 2 before you do the job.